In general, a blood purification apparatus such as a dialyzer is used in hemodialysis treatment. A dialysate supplying line, to supply the dialysate, as well as a dialysate discharge line, to discharge the waste dialysate, is connected to the blood purification apparatus. The dialysate supply line and dialysate discharge line extend from a dialysis apparatus main body and are connected to the blood purification apparatus to supply the dialysate to the blood purification apparatus and to discharge the waste dialysate from the blood purification apparatus to the outside.
The reciprocation pump (duplex pump) is connected to the dialysis apparatus main body across the dialysate supply line and the dialysate discharge line. As shown in FIGS. 6 and 7, the reciprocation pump includes a casing 101 that reciprocatably accommodates a plunger 102. A supply liquid-side pumping chamber P1 and a waste liquid-side pumping chamber P2 are formed by the plunger 102 within the casing 101. Supply liquid-side ports 105, 106 communicate with the supply liquid-side pumping chamber P1. Waste liquid-side ports 107, 108 communicate with the waste liquid-side pumping chamber P2. A motor M reciprocates the plunger 102.
The supply liquid-side ports 105, 106 are provided with check valves V1, V2, respectively. The waste liquid-side ports 107, 108 are also provided with check valves V3, V4, respectively. The reciprocation pump is structured so that the supply liquid-side pumping chamber P1 sucks the liquid (dialysate) from its source through the supply liquid-side port 105. The chamber P1 supplies the dialysate to a blood purification apparatus (not shown in FIGS. 6 and 7) through the supply liquid-side port 106. The waste liquid-side pumping chamber P2 receives the waste liquid (waste dialysate) from the blood purification apparatus through the waste liquid-side port 107 and discharges it through the waste liquid-side port 108 to the outside.
An eccentric cam 103 is mounted on an output shaft Ma of the motor M. A block 104, reciprocated by the eccentric cam 103, is mounted on the plunger 102. With the motor M driving, the plunger 102 can be reciprocated via the block 104. The supply and discharge of the dialysate can be performed as described above. Such a reciprocation pump is disclosed in Japanese Laid-open Patent Publication No. 2003-284772.
However, in such a prior art reciprocation pump, shown in FIGS. 6 and 7, it requires a motor casing 101a for mounting the motor Mon the pump casing 101. Also, it requires sealing members S1, S2 interposed between the motor casing 101a and the pump casing 101. Thus, it is believed that the dialysate to be supplied to the blood purification apparatus and the waste dialysate would leak to the outside of the reciprocation pump due to aged degradation of the sealing members S1, S2. Such a problem is also found in reciprocal pumps in other fields that supply liquids to objective apparatus other than blood purification apparatus.